Item of Clothing The invention pertains to an item of clothing which at least partially covers the body of the wearer and comprises a back part. Clothing serves to protect the wearer, and in particular it serves to protect the wearer from the weather. At the same time, clothing has the task of providing means by which an adequate body temperature can be maintained. This means that the clothing maintains a normal body temperature during periods of little physical activity and thus prevents the body from cooling; during more strenuous physical activities, furthermore, clothing should provide a heat regulation function, which prevents the body temperature from rising. In addition to the actual body temperature, however, the perceived body tem perature is also crucial to the performance capacity of a human being, because a consid erable decrease in performance can be observed when a person perceives that he is overheated or has become cold. The body's temperature sensors, which are distributed over the entire body, play a decisive role here. These temperature sensors tell the person how warm or cold certain areas of the body are. This information is sent by the sensors to the brain, which then, if the sensors detect a feeling of cold, initiates appropriate measures, such as stimulating the metabolism, which has the effect of converting the energy reserves of the body into heat and thus of increasing the body's temperature. Conversely, when a person feels overheated, the metabolism can be reduced in order to lower the body temperature. The primary information carrier of the human body is the spinal column. The spinal column also plays the most important role in relation to the determination of body temperature and of the overall sense of well-being. To put in simply, the spinal column is the main temperature sensor of the human body. As a result, the temperature deter mined in the area of the spinal column is decisive for the entire organism with respect to both the performance capacity of the body and the feeling of well-being. For this rea son, it is of crucial importance to be able to influence the temperature of the body in the area of the spinal column as a way of achieving certain results. Past approaches have been based on the theory that clothing in the area of the spinal column should be de signed in such a way as to dissipate heat. This theory is based on the assumption that, especially during strenuous physical activity, the human being begins to sweat and thus the body temperature increases. Through the dissipation of the heat in the area of the spinal column, the temperature sensors present there detect a less pronounced tempera ture increase than would be the case if no heat were dissipated from the area of the spi nal column. As a result, the brain does not conclude that the body is overheated; in stead, it merely determines a slight temperature increase, and therefore the metabolism can remain on the same high level. The present invention takes a different approach: A person's feeling of well being depends to a large extent on the perceived temperature. This means that, regard less of how low the temperature of the environment may be, the person will still feel comfortable as long as the clothing around him keeps him sufficiently warm. It is true that human temperature sensors are distributed over the entire body; but because the spi nal column represents the primary temperature sensor, as explained above, it is possible to exert an influence on the feeling of well-being by producing changes in the area of the 3 spinal column in particular. Because the performance capacity of a human being also depends on psychological components, one of which pertains to the feeling of well being with respect to temperature, influencing the perceived temperature in the area of the spinal column is a highly suitable way of increasing the performance capacity of the human being. This influence, in contrast to the old theory, can also be achieved by sug gesting to the spinal column area of the body that the temperature is higher than is actu ally the case. Especially during the cold season, an influence of this type leads to a maximum of mobility and performance capacity, because the body is not subjected to the additional stress associated with a stimulated metabolism during periods of per ceived low temperatures. Instead, influencing the perceived temperature in the area of the spinal column can lead to a conservation of energy, because the body is not forced to stimulate internal metabolism in order to increase the body temperature. Instead, me tabolism can remain on the same level, so that the energy otherwise required to stimulate it is available to the body for physical performance. It is therefore the goal of the present invention to provide an item of clothing which makes it possible to influence the temperature in the area of the spinal column in such a way that the temperature sensors of the body in the area of the spinal column de tect a temperature which is higher than the actual body temperature determined at other points of the body. According to the invention, this goal is achieved in that the back part comprises a thermal insulation element, which extends along the spinal column and cov ers at least the area of the thoracic vertebrae. The invention creates an item of clothing which exerts an influence on tempera ture in the area of the spinal column of the human being. The thermal insulation ele ment arranged on the back part of the item of clothing extends over the area of the spinal column and makes it difficult for heat to escape through the clothing in this area. As a result, the heat sensors of the body located in the area of the spinal column transmit a higher body temperature to the brain. Especially in the cold season or during winter sports activities, this leads to a positive effect on the sense of well-being, because the brain receiving the information assumes that the temperature is higher that it actually is, which has the effect of exerting a positive influence on the person's mental state. Be cause the sense of physical well-being has considerable influence on a person's per formance capacity, the result is improved performance. In an elaboration of the invention, the thermal insulation element is thicker than the rest of the material. This makes it possible to achieve a good thermal insulation ef fect. At the same time, this greater thickness can be achieved by simply sewing several layers of the material forming the item of clothing on top of each other. This means that there is no need to use additional materials, and as a result the cost of the inventive item of clothing is low. In another elaboration of the invention, the thermal insulation element is denser than the rest of the material. In this way, too, it is possible to achieve the positive inven tive effects while simultaneously simplifying the production of the thermal insulation element. The greater density can be obtained, for example, by using a more closely stitched style of knitting, which can be easily incorporated into the process used to pro duce the inventive item of clothing. It is advantageous to arrange areas of heat-regulating material next to the thermal insulation material. By providing heat-regulating material near the thermal insulation 4 C. NRP blCC\CABW65041_1 DOC-3112012 element, it is possible to prevent the body from becoming overheated. This is explained by the fact that, when the body temperature is rising very quickly, the heat can spread out beyond the area of the thermal insulation element. When the area of the heat-regulating material is reached, the excess heat can then dissipate, and thus the temperature is prevented from increasing beyond a certain performance-lowering level. According to one aspect, the present invention provides an item of clothing which at least partially covers the body of the wearer and includes a back part, wherein the back part has a thermal insulation element which is an elongated, vertically oriented strip that extends along the spinal column and covers at least the area of the thoracic vertebrae, wherein said back part includes elongated, vertically oriented strips of heat-regulating material which are arranged next to the thermal insulation element and are parallel thereto. Other elaborations and embodiments of the invention are indicated in the other subclaims. An exemplary embodiment of the invention is illustrated in the drawing and described below in detail. Figure 1 shows a perspective diagram of the back of an inventive item of clothing; Figure 2 shows a perspective diagram of a different design of the back of an inventive item of clothing; Figure 3 shows a cross section along line III-III of Figure 1; and Figure 4 shows a view of the detail marked "X" in Figure 2. The item of clothing selected as the exemplary embodiment is a short-sleeved T-shirt. The shirt partially covers the body of the wearer; the lower arms and the neck of the wearer are not covered. The item of clothing has a back part 2, which comprises a thermal insulation element 3. The thermal insulation element 3 extends along the spinal column of the wearer. In the exemplary embodiment, it is in the form of a vertically oriented strip. In the exemplary embodiment, the thermal insulation element extends from the neck opening of the item of clothing to the bottom end opposite the neck opening and thus extends over the entire length of the spinal column except for the cervical vertebrae. According to the invention, coverage is provided at least in the area of the thoracic vertebrae, which are located between the seven cervical vertebrae and the five lumbar vertebrae. Because these thoracic vertebrae constitute the major part of the spinal column, covering this area of the spinal column is sufficient to achieve the advantageous effect of the invention. Expanding the area as shown in the embodiments according to Figures 1 and 2, for example, makes it possible to improve the effect even more. The thermal insulation element 3 is thicker than the rest of the material of the item of clothing. This greater thickness is achieved in the exemplary embodiment according to Figure 1 by knitting several layers 31 of material on top of each other. As can be derived from Figure 3, three layers 31 are arranged on top of each other in the exemplary embodiment. What is involved therefore is a multi-layer configuration of the thermal insulation element 3. In the exemplary embodiment according to Figure 2, the thermal insulation element 3 is denser than the rest of the material of the item of 5 C:\NRPorbl\DCC\CAB\465418_1 DOC-2/1012012 clothing. This greater density can be achieved by using a more closely-stitched style of knitting for the thermal insulation element 3 than that used for the rest of the material of the item of clothing. As can be seen in Figure 4, the thermal insulation element 3 can also be produced by using additional materials. For this purpose, additional threads 33, 34 are incorporated into the knitting in addition to the base thread 32, which has the result of increasing the density. Additional yarns with special properties can also be used, such as, for example, yarns which are coated with a noble metal such as gold or silver. The use of additional yarns also makes it possible to achieve a greater density or a greater thickness; simultaneously, the use of the noble metals has the effect of reflecting the heat radiating from the body. In the exemplary embodiment according to Figure 2, areas 4 of heat-regulating material are arranged next to the thermal insulation element 3. The areas 4 of heat regulating material can consist of knitted mesh fabric, for example. When mesh fabric is used, only 80% of the skin is covered by the selected yarn; as a result of the openings in the fabric, air can be exchanged and thus the heat level can be regulated. Other designs for the areas 4 of heat-regulating material are also possible. Thus, a fabric with a wavy structure can be provided, such that only individual points of the fabric make contact with the skin. This design also offers the advantage that sweat can be carried away to the outside surface of the item of clothing via the points in contact with the skin, as a result of which the comfort with which the inventive item of clothing can be worn is additionally improved. In a modification of the exemplary embodiment, the item of clothing can also be designed as a singlet or as a shirt with shoulder straps. The inventive thermal insulation element can also be used on jackets and overalls. The only essential point is that it must cover at least the area of the thoracic vertebrae of the spinal column on the back of the wearer in order to bring about the positive effect on the temperature sensors of the skin. Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as, an acknowledgement or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. 6